This invention relates in general to microprocessor based computers specially designed for use in industrial applications and mission-critical environments, and in particular to such having passive I/O (input/output) backplanes into which is plugged a microprocessor based, single-board computer, i.e. a "CPU card", and in particular to such passive backplanes which have signal lines and connectors for coupling peripherals to a plugged-in CPU card according to I/O bus standards commonly found in INTEL PENTIUM based personal computers, e.g. I/O buses conforming to the ISA (industry standard adapter) and PCI (peripheral component interconnect) standards.
This invention particularly addresses a problem that has arisen in the PICMG (PCI Industrial Computer Manufacturers Group) industry with the introduction of the INTEL PENTIUM II, the "PICMG industry" being the makers and users of industrial and mission-critical computers that are compliant with the PICMG specification for industrial PCI/ISA passive backplanes and CPU cards. Due immediately the size, weight and form of the PENTIUM II and its mounting and cooling hardware, it should not be mounted on a conventional PICMG CPU card.
The development of PICMG computers based on passive backplane technology has been driven by the needs of the industrial and Computer-Telephony Integration (CTI) markets. Personal computers designed for desktop use are based on motherboard architectures which fail to address a number of important requirements for industrial and CTI use. For example, a motherboard structure is inflexible and may require the replacement of the entire motherboard in order to repair or to upgrade the system. This results in long system downtime which may be tolerable in a system used for office applications, but which is totally unacceptable in a system which controls the core processes on which a manufacturing business depends.
Also, many industrial and CTI applications require a large number of expansion slots for real-world I/O or speech cards. These are not available on motherboard-based computers. Additionally, the overall construction of the motherboard and I/O expansion board system is not designed to cope with the harsh environmental demands of many industrial applications.
A passive-backplane architecture solves these problems by completely dispensing with the motherboard. In a passive backplane computer, a system bus is used to couple a plug-in CPU card with a plurality of plug-in add-on cards. This architecture makes rapid repair by card substitution possible, and system upgrades and changes are greatly simplified, with minimum system downtime. With a passive backplane there is also considerable capacity for system expansion, and the rugged construction of a typical passive backplane system provides reliable operation in an industrial environment.
Because of the advantages of a passive backplane and a plug-in CPU card, and because there was no configuration standard for PCI buses, a group of industrial computer product vendors, with a long history of developing PC architecture products for industrial use joined forces, and in 1994 they established the PCI Industrial Computer Manufacturers Group (PICMG) with the mission to define an industrial PCI/ISA passive backplane and CPU card interface specification. The result was a comprehensive specification for a passive backplane architecture to support both PCI and ISA I/O buses, the PCI/ISA industrial standard.
The PCI/ISA industrial standard specifies the logical and mechanical interface between the CPU card and the passive backplane. Instead of using a redesigned edge connector for the CPU card, the PICMG technical committee chose a physical board format and connector based on the ISA adapter specification and added a PCI connector below, and in line with, the ISA connector, allowing sufficient space for 32-bit or 64-bit PCI interfaces. Thus a prior art PICMG CPU card and backplane physical connection consists of an ISA connector in line with a PCI connector.
Prior art PICMG CPU cards typically include a microprocessor, e.g. a PENTIUM microprocessor, and certain features, for example: read only memory (ROM), random access memory (RAM), a video controller, some I/O controllers and connectors, a video controller, and a processor "chip set" which controls and times communications between the microprocessor and the other components of the card and the backplane I/O buses. Conventionally a PICMG backplane is oriented horizontally, i.e. face up, in a rack-mounted frame and the CPU card plugs vertically into the backplane. When plugged-in, the CPU card is coupled to a plurality of additional ISA and PCI connectors, via the backplane, for communicating with add-on cards. A CPU card plugged into a passive backplane can be swapped out very quickly as opposed to the difficulty of swapping out a PC motherboard. This fast CPU swappability is a major advantage of a PICMG computer.
With the advent of the PENTIUM II microprocessor and its much larger overall outline and mass, mounting a PENTIUM II on a vertically-installed CPU card creates special problems. The new SECC (Single Edge Contact Cartridge) connector used to edge mount the PENTIUM II is a wide variant from conventional on-board processor sockets, and because of power dissipation specifications of approximately 35 Watts, the PENTIUM II requires a massive heat sink and cooling system. Incorporating the PENTIUM II into an industrial file or communication server without the Intel recommended cooling fan and heat sink, or other properly engineered cooling system, would be inviting disaster. However with the INTEL recommended fan and heatsink combination, the PENTIUM II and its associated hardware weighs more than one-half pound (11 oz) and is about 24 cubic inches in volume (5.5" L.times.1.75" D.times.2.5" H). Also per an INTEL product information sheet, specified fan/heatsink supports must be used, whether the processor has an active or a passive fan/heatsink. Therefore, to use a PENTIUM II in the industrial arena, provisions must be made for mounting and supporting the PENTIUM II with its associated hardware to ensure reliable operation under industrial conditions of shock and vibration as well as to insure survival during normal shipment or transport.
For all these reasons, mounting a PENTIUM II on a CPU card that is plugged vertically into an edge connector, as has been the PICMG method, is not acceptable. Special bracing would be needed to prevent damage due to stress caused by the mass combined with a center of gravity so far from the board. Long term stress would likely cause damage but also if the unit is dropped, the moment of force created by the large PENTIUM II and its associated hardware could easily cause fractures in leads and solder joints.
This invention is a solution to these problems. This invention has a passive backplane, a feature card, a PENTIUM II, and a voltage regulator module (VRM). Connectors on the backplane allow the PENTIUM II, the feature card and the VRM to be plugged into the backplane separately. The feature card contains features such as memory, processor chip set, and I/O currently found on typical PICMG CPU cards. The PENTIUM II is not mounted on a plug-in card. It is vertically plugged into the backplane so that support means beyond the INTEL recommended retaining hardware are not necessary. Likewise, the VRM is vertically plugged into the backplane with traces in the backplane connecting the feature card, VRM and PENTIUM II as necessary. With this design the entire CPU and associated features can be quickly swapped out as in prior art PICMG computers, the difference being that they reside in three pieces, each separately plugged into the backplane.
Having the PENTIUM II separately pluggable into the backplane is advantageous in other ways. It permits the proper orientation and support of the processor as well as providing sufficient room for cooling air flow. The GTL+ bus permits the routing of the processor signals up from the backplane without signal degradation due to the incorporated termination scheme. It permits critical placement of the PENTIUM II, VRM and feature card on the backplane to ensure signal integrity and minimal power loss by minimizing and simplifying the routing and power distribution of the GTL+ bus and the power planes. Mean time to repair (MTTR) does not suffer because there are no more active components "soldered down" to the backplane than in any single board computer design. The processor, the VRM and the feature set are all in sockets designed for withstanding industrial and commercial applications.
Other advantages and attributes of this invention will be readily discernable upon a reading of the text hereinafter.